2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
26 /// Simple macro to wrap a very common while loop, no facny, no flexibility,
27 /// hardcoded names 'mlist' and 'from'.
28 #define SERIALIZE(b) while (b) (*mlist++).move = make_move(from, pop_1st_bit(&b))
30 /// Version used for pawns, where the 'from' square is given as a delta from the 'to' square
31 #define SERIALIZE_PAWNS(b, d) while (b) { Square to = pop_1st_bit(&b); \
32 (*mlist++).move = make_move(to - (d), to); }
35 template<CastlingSide Side, bool OnlyChecks>
36 MoveStack* generate_castle(const Position& pos, MoveStack* mlist, Color us) {
38 CastleRight cr = CastleRight((Side == KING_SIDE ? WHITE_OO : WHITE_OOO) << us);
40 if (pos.castle_impeded(us, Side) || !pos.can_castle(cr))
43 // After castling, the rook and king final positions are the same in Chess960
44 // as they would be in standard chess.
45 Square kfrom = pos.king_square(us);
46 Square kto = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
47 Square rfrom = pos.castle_rook_square(us, Side);
48 Bitboard enemies = pos.pieces(~us);
50 assert(!pos.in_check());
52 for (Square s = std::min(kfrom, kto), e = std::max(kfrom, kto); s <= e; s++)
53 if ( s != kfrom // We are not in check
54 && (pos.attackers_to(s) & enemies))
57 // Because we generate only legal castling moves we need to verify that
58 // when moving the castling rook we do not discover some hidden checker.
59 // For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
60 if ( pos.is_chess960()
61 && (pos.attackers_to(kto, pos.pieces() ^ rfrom) & enemies))
64 (*mlist++).move = make_castle(kfrom, rfrom);
66 if (OnlyChecks && !pos.move_gives_check((mlist - 1)->move, CheckInfo(pos)))
73 template<Square Delta>
74 inline Bitboard move_pawns(Bitboard p) {
76 return Delta == DELTA_N ? p << 8
77 : Delta == DELTA_S ? p >> 8
78 : Delta == DELTA_NE ? (p & ~FileHBB) << 9
79 : Delta == DELTA_SE ? (p & ~FileHBB) >> 7
80 : Delta == DELTA_NW ? (p & ~FileABB) << 7
81 : Delta == DELTA_SW ? (p & ~FileABB) >> 9 : 0;
85 template<MoveType Type, Square Delta>
86 inline MoveStack* generate_promotions(MoveStack* mlist, Bitboard pawnsOn7, Bitboard target, Square ksq) {
88 Bitboard b = move_pawns<Delta>(pawnsOn7) & target;
92 Square to = pop_1st_bit(&b);
94 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
95 (*mlist++).move = make_promotion(to - Delta, to, QUEEN);
97 if (Type == MV_QUIET || Type == MV_EVASION || Type == MV_NON_EVASION)
99 (*mlist++).move = make_promotion(to - Delta, to, ROOK);
100 (*mlist++).move = make_promotion(to - Delta, to, BISHOP);
101 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
104 // Knight-promotion is the only one that can give a direct check not
105 // already included in the queen-promotion.
106 if (Type == MV_QUIET_CHECK && (StepAttacksBB[W_KNIGHT][to] & ksq))
107 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
109 (void)ksq; // Silence a warning under MSVC
116 template<Color Us, MoveType Type>
117 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq = SQ_NONE) {
119 // Compute our parametrized parameters at compile time, named according to
120 // the point of view of white side.
121 const Color Them = (Us == WHITE ? BLACK : WHITE);
122 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
123 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
124 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
125 const Square UP = (Us == WHITE ? DELTA_N : DELTA_S);
126 const Square RIGHT = (Us == WHITE ? DELTA_NE : DELTA_SW);
127 const Square LEFT = (Us == WHITE ? DELTA_NW : DELTA_SE);
129 Bitboard b1, b2, dc1, dc2, emptySquares;
131 Bitboard pawnsOn7 = pos.pieces(PAWN, Us) & TRank7BB;
132 Bitboard pawnsNotOn7 = pos.pieces(PAWN, Us) & ~TRank7BB;
134 Bitboard enemies = (Type == MV_EVASION ? pos.pieces(Them) & target:
135 Type == MV_CAPTURE ? target : pos.pieces(Them));
137 // Single and double pawn pushes, no promotions
138 if (Type != MV_CAPTURE)
140 emptySquares = (Type == MV_QUIET ? target : ~pos.pieces());
142 b1 = move_pawns<UP>(pawnsNotOn7) & emptySquares;
143 b2 = move_pawns<UP>(b1 & TRank3BB) & emptySquares;
145 if (Type == MV_EVASION) // Consider only blocking squares
151 if (Type == MV_QUIET_CHECK)
153 b1 &= pos.attacks_from<PAWN>(ksq, Them);
154 b2 &= pos.attacks_from<PAWN>(ksq, Them);
156 // Add pawn pushes which give discovered check. This is possible only
157 // if the pawn is not on the same file as the enemy king, because we
158 // don't generate captures. Note that a possible discovery check
159 // promotion has been already generated among captures.
160 if (pawnsNotOn7 & target) // Target is dc bitboard
162 dc1 = move_pawns<UP>(pawnsNotOn7 & target) & emptySquares & ~file_bb(ksq);
163 dc2 = move_pawns<UP>(dc1 & TRank3BB) & emptySquares;
170 SERIALIZE_PAWNS(b1, UP);
171 SERIALIZE_PAWNS(b2, UP + UP);
174 // Promotions and underpromotions
175 if (pawnsOn7 && (Type != MV_EVASION || (target & TRank8BB)))
177 if (Type == MV_CAPTURE)
178 emptySquares = ~pos.pieces();
180 if (Type == MV_EVASION)
181 emptySquares &= target;
183 mlist = generate_promotions<Type, RIGHT>(mlist, pawnsOn7, enemies, ksq);
184 mlist = generate_promotions<Type, LEFT>(mlist, pawnsOn7, enemies, ksq);
185 mlist = generate_promotions<Type, UP>(mlist, pawnsOn7, emptySquares, ksq);
188 // Standard and en-passant captures
189 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
191 b1 = move_pawns<RIGHT>(pawnsNotOn7) & enemies;
192 b2 = move_pawns<LEFT >(pawnsNotOn7) & enemies;
194 SERIALIZE_PAWNS(b1, RIGHT);
195 SERIALIZE_PAWNS(b2, LEFT);
197 if (pos.ep_square() != SQ_NONE)
199 assert(rank_of(pos.ep_square()) == relative_rank(Us, RANK_6));
201 // An en passant capture can be an evasion only if the checking piece
202 // is the double pushed pawn and so is in the target. Otherwise this
203 // is a discovery check and we are forced to do otherwise.
204 if (Type == MV_EVASION && !(target & (pos.ep_square() - UP)))
207 b1 = pawnsNotOn7 & pos.attacks_from<PAWN>(pos.ep_square(), Them);
212 (*mlist++).move = make_enpassant(pop_1st_bit(&b1), pos.ep_square());
220 template<PieceType Pt>
221 inline MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist,
222 Color us, const CheckInfo& ci) {
223 assert(Pt != KING && Pt != PAWN);
227 const Square* pl = pos.piece_list(us, Pt);
231 target = ci.checkSq[Pt] & ~pos.pieces(); // Non capture checks only
236 if ( (Pt == BISHOP || Pt == ROOK || Pt == QUEEN)
237 && !(PseudoAttacks[Pt][from] & target))
240 if (ci.dcCandidates && (ci.dcCandidates & from))
243 b = pos.attacks_from<Pt>(from) & target;
245 } while (*++pl != SQ_NONE);
252 template<PieceType Pt>
253 FORCE_INLINE MoveStack* generate_moves(const Position& pos, MoveStack* mlist,
254 Color us, Bitboard target) {
255 assert(Pt != KING && Pt != PAWN);
259 const Square* pl = pos.piece_list(us, Pt);
264 b = pos.attacks_from<Pt>(from) & target;
266 } while (*++pl != SQ_NONE);
273 FORCE_INLINE MoveStack* generate_moves<KING>(const Position& pos, MoveStack* mlist,
274 Color us, Bitboard target) {
275 Square from = pos.king_square(us);
276 Bitboard b = pos.attacks_from<KING>(from) & target;
284 /// generate<MV_CAPTURE> generates all pseudo-legal captures and queen
285 /// promotions. Returns a pointer to the end of the move list.
287 /// generate<MV_QUIET> generates all pseudo-legal non-captures and
288 /// underpromotions. Returns a pointer to the end of the move list.
290 /// generate<MV_NON_EVASION> generates all pseudo-legal captures and
291 /// non-captures. Returns a pointer to the end of the move list.
293 template<MoveType Type>
294 MoveStack* generate(const Position& pos, MoveStack* mlist) {
296 assert(Type == MV_CAPTURE || Type == MV_QUIET || Type == MV_NON_EVASION);
297 assert(!pos.in_check());
299 Color us = pos.side_to_move();
302 if (Type == MV_CAPTURE)
303 target = pos.pieces(~us);
305 else if (Type == MV_QUIET)
306 target = ~pos.pieces();
308 else if (Type == MV_NON_EVASION)
309 target = ~pos.pieces(us);
311 mlist = (us == WHITE ? generate_pawn_moves<WHITE, Type>(pos, mlist, target)
312 : generate_pawn_moves<BLACK, Type>(pos, mlist, target));
314 mlist = generate_moves<KNIGHT>(pos, mlist, us, target);
315 mlist = generate_moves<BISHOP>(pos, mlist, us, target);
316 mlist = generate_moves<ROOK>(pos, mlist, us, target);
317 mlist = generate_moves<QUEEN>(pos, mlist, us, target);
318 mlist = generate_moves<KING>(pos, mlist, us, target);
320 if (Type != MV_CAPTURE && pos.can_castle(us))
322 mlist = generate_castle<KING_SIDE, false>(pos, mlist, us);
323 mlist = generate_castle<QUEEN_SIDE, false>(pos, mlist, us);
329 // Explicit template instantiations
330 template MoveStack* generate<MV_CAPTURE>(const Position& pos, MoveStack* mlist);
331 template MoveStack* generate<MV_QUIET>(const Position& pos, MoveStack* mlist);
332 template MoveStack* generate<MV_NON_EVASION>(const Position& pos, MoveStack* mlist);
335 /// generate<MV_QUIET_CHECK> generates all pseudo-legal non-captures and knight
336 /// underpromotions that give check. Returns a pointer to the end of the move list.
338 MoveStack* generate<MV_QUIET_CHECK>(const Position& pos, MoveStack* mlist) {
340 assert(!pos.in_check());
342 Color us = pos.side_to_move();
344 Bitboard dc = ci.dcCandidates;
348 Square from = pop_1st_bit(&dc);
349 PieceType pt = type_of(pos.piece_on(from));
352 continue; // Will be generated togheter with direct checks
354 Bitboard b = pos.attacks_from(Piece(pt), from) & ~pos.pieces();
357 b &= ~PseudoAttacks[QUEEN][ci.ksq];
362 mlist = (us == WHITE ? generate_pawn_moves<WHITE, MV_QUIET_CHECK>(pos, mlist, ci.dcCandidates, ci.ksq)
363 : generate_pawn_moves<BLACK, MV_QUIET_CHECK>(pos, mlist, ci.dcCandidates, ci.ksq));
365 mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, ci);
366 mlist = generate_direct_checks<BISHOP>(pos, mlist, us, ci);
367 mlist = generate_direct_checks<ROOK>(pos, mlist, us, ci);
368 mlist = generate_direct_checks<QUEEN>(pos, mlist, us, ci);
370 if (pos.can_castle(us))
372 mlist = generate_castle<KING_SIDE, true>(pos, mlist, us);
373 mlist = generate_castle<QUEEN_SIDE, true>(pos, mlist, us);
380 /// generate<MV_EVASION> generates all pseudo-legal check evasions when the side
381 /// to move is in check. Returns a pointer to the end of the move list.
383 MoveStack* generate<MV_EVASION>(const Position& pos, MoveStack* mlist) {
385 assert(pos.in_check());
388 Square from, checksq;
390 Color us = pos.side_to_move();
391 Square ksq = pos.king_square(us);
392 Bitboard sliderAttacks = 0;
393 Bitboard checkers = pos.checkers();
397 // Find squares attacked by slider checkers, we will remove them from the king
398 // evasions so to skip known illegal moves avoiding useless legality check later.
403 checksq = pop_1st_bit(&b);
405 assert(color_of(pos.piece_on(checksq)) == ~us);
407 switch (type_of(pos.piece_on(checksq)))
409 case BISHOP: sliderAttacks |= PseudoAttacks[BISHOP][checksq]; break;
410 case ROOK: sliderAttacks |= PseudoAttacks[ROOK][checksq]; break;
412 // If queen and king are far or not on a diagonal line we can safely
413 // remove all the squares attacked in the other direction becuase are
414 // not reachable by the king anyway.
415 if (squares_between(ksq, checksq) || !(PseudoAttacks[BISHOP][checksq] & ksq))
416 sliderAttacks |= PseudoAttacks[QUEEN][checksq];
418 // Otherwise we need to use real rook attacks to check if king is safe
419 // to move in the other direction. For example: king in B2, queen in A1
420 // a knight in B1, and we can safely move to C1.
422 sliderAttacks |= PseudoAttacks[BISHOP][checksq] | pos.attacks_from<ROOK>(checksq);
429 // Generate evasions for king, capture and non capture moves
430 b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
434 // Generate evasions for other pieces only if not under a double check
438 // Blocking evasions or captures of the checking piece
439 target = squares_between(checksq, ksq) | checkers;
441 mlist = (us == WHITE ? generate_pawn_moves<WHITE, MV_EVASION>(pos, mlist, target)
442 : generate_pawn_moves<BLACK, MV_EVASION>(pos, mlist, target));
444 mlist = generate_moves<KNIGHT>(pos, mlist, us, target);
445 mlist = generate_moves<BISHOP>(pos, mlist, us, target);
446 mlist = generate_moves<ROOK>(pos, mlist, us, target);
447 return generate_moves<QUEEN>(pos, mlist, us, target);
451 /// generate<MV_LEGAL> generates all the legal moves in the given position
454 MoveStack* generate<MV_LEGAL>(const Position& pos, MoveStack* mlist) {
456 MoveStack *last, *cur = mlist;
457 Bitboard pinned = pos.pinned_pieces();
459 last = pos.in_check() ? generate<MV_EVASION>(pos, mlist)
460 : generate<MV_NON_EVASION>(pos, mlist);
462 if (!pos.pl_move_is_legal(cur->move, pinned))
463 cur->move = (--last)->move;